Just about all reality shows - tho I might allow Big Brother back if it was run under series 1 UK rules, where they actually had a range of people, and left them to get on with it, instead of getting a dozen fame hungry clones and giving them tasks every hour in case someone stops watching.
Bring back the only reality show I ever liked and was worth it, Kings of Comedy.
I don't know if the US had the same 'thing' as us, with the breaking of alternative comedy in the 80s, they took 6 old style comedians from the 70s, and 6 'new' , on the up comics, and put them in a house together, and there was genuinely interesting conversations about everything, because you've got a dozen smart, witty people instead of the usual dozen dumbasses.
Also, as the BBC brought back 'Not Going Out' (a miracle as it's genuinely good and popular), I'd have to ask for 'The Late Edition' to return, it was essentially the UK's 'Daily Show' hosted by Marcus Brigstocke.